Space surveyor Gaia: the story continues

Surveying space

After a little more than a year on the job of creating an accurate 3D map of the Milky Way, space surveyor Gaia has taken more than 150 billion images, including star pictures and spectra. Despite some performance challenges posed by basic angle issues and stray light, Gaia has observed light variations of stars beyond the Milky Way, 160,000 light years away. If Gaia keeps working as well as it is, four more years could well be added to the mission, which would significantly improve the accuracy of the data.

Designed and built by Airbus Defence and Space for the European Space Agency (ESA), Gaia was launched on 19 December 2013. It’s mission: to conduct a census of a billion stars and other astronomical phenomena in our galaxy to help scientists solve the mystery of stellar evolution and star formation and provide new insights into the origin and formation history of the Milky Way.

To ensure that Gaia would be able to face the rigours of space travel, Airbus Defence and Space created the largest instrument ever fully built in silicon carbide for this mission. This lightweight, rigid ceramic material can withstand just about anything. The company’s engineers have extensive experience with this material, gained from creating the silicon carbide telescopes on the Herschel telescope and the Aladin instrument for the ESA wind satellite Aeolus, scheduled to launch in 2016, as well as on three Earth observation satellites. To protect both spacecraft and payload instruments from the extreme variations in temperature, the scientists and engineers also created Gaia’s sunshield, which allows thermal isolation performance at extreme temperatures between -170°C and +70°C.

Airbus Defence and Space teams continue to support Gaia’s in-flight operations throughout the mission with up-to-date software that tests, monitors and analyses Gaia’s performance and behaviour. The scientists are also using dedicated software to solve the remaining performance and processing challenges posed by the hardware.

The spacecraft is equipped with a digital camera with more than one billion pixels, making it the largest in space today. Subsequently, Gaia can detect celestial objects 400,000 times fainter than the human eye can see. The camera is so precise that if it were on the moon, it could offer the ability to measure the thumbnail of a person on Earth.

Constantly spinning at the Lagrange point L2, 1.5 million km behind Earth, Gaia clocks more than 40 million observations a day. Since the start of its operational phase, Gaia has downloaded an average of 40 Gigabytes per day to the ground segment on Earth. It has also sent 240 alerts, signalling the detection of transient cosmic phenomena, including, in August 2014, a supernova – the explosion of a star.

As it is programmed to measure the position of each star repeatedly, about 70 times during its five-year mission, it will be able to track their motions through the galaxy and the variation of their brightness if any.

It will also examine the light of stars bent by a huge mass, a phenomenon predicted by Albert Einstein which was first observed close to the Sun by Sir Eddington during a solar eclipse in 1919. Gaia does not look directly at the Sun to protect its instruments, but it is so accurate that it can measure this phenomenon with a mass 1 000 times lighter like the planet Jupiter.

Not long ago, a local cosmic celebrity was spotted by Gaia: Comet 67P/Churyumov-Gerasimenko, currently accompanied by another Airbus Defence and Space built spacecraft, namely Rosetta. The image shows the comet’s coma and tail. The nucleus and Rosetta, which was some 300 km from the surface at the time, are both hidden in the innermost pixel.